Shock the Monkey

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By now many of you have seen the CSI episode a few months ago called “Unshockable”, which featured the country band Rascal Flatts. Now, I normally don’t watch CSI, but seeing the trailers earlier in the week for this episode sure got my curiosity up. So I emailed all my electrical engineering buddies to watch the show and we compared notes.

And sure enough, it was bad. Way bad in fact. So filled with misconceptions and flat-out exaggerations about how people get shocked and electrocuted, that their bass player Jay Demarcus should do a PSA explaining what getting shocked on stage is really like. In the CSI story, Jay gets shocked and knocked out when he touches his guitar and microphone at the some time. This dasterdly deed was done by an aging guitar tech who wanted a chance to play bass onstage so he could get lucky with the ladies. What a plot line!

But the real craziness was the artistic license the director took to “show” the shock. There literally were blue sparks coming out from around Jay’s lips, sort of a halo of electricity. He then looses his memory, and can’t remember the other guys in the band. But perhaps the worse of all possible side effects is that he starts hating country music, and switches to rap. No kidding. If I would have know that rapping was a side effect of being shocked, perhaps that could have stopped some of the horrible country bands who played in our local clubs….

During the investigative part of the drama with all the forensic scientists looking for a cause of the “accident” they explain and show how the guitar strings had burned flesh embedded from the “electrocution”. Plus we get to see an XLR cable with a big arc mark down the side of the barrel where “the voltage arc jumped across”. Then the real “shocker” came with the explanation that Jay’s brain damage that resulted in amnesia couldn’t have been from “only” 120 volts. They postulated that it was juiced up to 240 volts. Gimme a break. The only way you get that sort of amnesia is electroshock therapy where your brain is zapped by electrodes in a medical procedure. But I suppose the writers were looking for a story line.

Let me clue you in about getting shocked on stage. There’s no blue lightning bolts around your lips, no singed flesh on the guitar strings, and there’s certainly no arc marks down the side of the XLR connectors. Nope… None of that. You jerk around a bit then simply fall over and pass out when your heart goes into fibrillation or stops beating and your buddies are telling you to stop kidding around. If someone’s smart enough to start CPR immediately and call 911, then you have a chance of living. If not, then you’re dead.

That’s the problem with getting shocked on stage. So many of us have been shocked from a guitar or mic that we don’t think it’s any big deal. And notice I said “shocked” and not “electrocuted”. Electrocution is what happens when you die from being shocked. So you can’t have been electrocuted and reading this blog. Yes, plenty of you have been shocked, as I have been dozens of times on stage. So we’re going to start an ongoing survey. Please comment and tell us if you’ve ever been shocked on stage by your guitar, microphone, mixing board, or whatever and how it happened. Hopefully you won’t ever be shocked like the guys in Rascal Flatts as there’s way too much bad rap perpetrated by white guys already.

And Rascal Flatts, if any of you guys are reading this, please contact us about doing a PSA to set the record straight about getting shocked on stage. Seriously…

8 Comments to “Shock the Monkey”

Thanks for the interesting articles. You have helped clarify a topic I work with weekly. I am a home handyman, so I am usually trying to repair items around the house. I have the 110-120 voltage part down pretty well, but now I need to learn more about the 220 voltage stuff since my new well pump is 220 instead of 110 volts. I am planning to install 220 volts for an arc welder some time this fall.
Your articles are clear and concise. I really appreciate the article on how to use a digital ohm-meter. Most books ( I have several) are written for someone who already knows the information. You make it understandable.

Isn’t your mixer grounded through your power amps? That is, you should have a shield connection from the output of the mixer to either your powered speakers or an amp feeding speakers. If those power amps aren’t grounded, and your mixer isn’t grounded, then you can get voltage creep up to 60 volts or more.

I would hookup only the mixer be itself without any speakers or amps hooked up to it, then meter from the mixer chassis to your ground pin on a power outlet. If you read zero volts (or a fraction of a volt) then something else that’s ungrounded is backfeeding voltage into your mixer causing the shock. If your mixer reads that 4 to 11 volts AC from its chassis to ground, then there’s something wrong in the power supply of the mixer itself. The reason I suspect your power amps are ungrounded is that a floated mixer would normally be grounded via the amps, and since it’s floating at 4 to 11 volts AC, then your amps must be floating as well. Please check that your amps are grounded and get back to me.

Thanks for the articles. We just purchased a new mixing board and are getting shocked at the mic while playing guitar. I get a reading of 4 – 11 Volts AC when touching a volt meter, one lead to the new mixer and the other lead to any thing metal on my Bass amp. All of my other equipment shows zero when I do this with anything but the new mixer. I returned the mixer and got another new one with the same results. Yamaha’s tech support is stumped and say they have never seen this problem. Also note that the new mixer does not have a three prong AC plug, just two. Yamaha says that the new technology doesn’t require a grounded plug.

Maybe I should look at another brand? BTW I checked all plugs in my house per your article and all are ok.

The mixer is most likely not the problem, I say this is in its design that is was allowed to be manufactured with a polerized two prong wall plug, it most likely has a system of double insulation/isolation from the supply power to the chassie, the problem is anything that is connected to this mixer board has a connection to its chassie through the shield in each audio cable connected to it, this may make it look like the problem is comming from the mixer but infact is one of the items/equipment that is connected to it, as Mike pointed out the grounded amps should have taken this voltage back down to a safe level, but there can be two reasons it didn’t ok three (amps unplugged LOL) if there is no grounding path for the amps, or if some kind of shield isolator has been put between the amp and mixer such as a hum eleminator, but lets look at what eles is connected to the mixer through audio cables, any DI’ed amps such as guitar, bass amp, keyboards<<very rarely a problem because of the isolated power supply, any other equipment that also has a connection with a 120 volt wall outlet? any one of these can be the source, if only the bass amp, then try disconnecting the audio connection to the mixer then messure if there is any voltage between the bass amp chassie and the wall ground or a known good ground if wall ground might be suspect, also check the chassie of the mixer to a known good ground to make sure it is clean, if you do have other equipment into or out of the mixer check each one to see if the voltage follows one, then you have something to start with, it might even be the amps, just make sure you lowere the gain on them before ever attempting to disconnect any audio cable going to a input to a amp.
Mike you have my E-mail or holler on the other site.

I hope this helps God Bless.
Wisdom so freely given by God so shall be freely given

I investigated a problem reported by a garage band a few years ago where their lead guitarist got a shock every time he touched both his guitar and his microphone when they were practicing in his basement. The problem turned out to be a floating ground caused by a sub panel installed before the code changed to require the ground and neutral to be isolated beyond the service entrance. The neutral connection in the main panel was loose, causing the potential of the neutral in the subpanel to float. Their PA was plugged in to an outlet on the main panel and the guitar amp was plugged in to the subpanel. This caused there to be a voltage between the ground prongs of each set of outlets and, thus the shields of both pieces of electronics. This was a great illustration of the reasoning for that code change and a reminder that there are still a large number of old installations out there that may hide this kind of surprises. It’s also a good reason to never do a gig without having your outlet tester and meter close at hand.

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